J.H. Alexander and P.K. Smith
Appropriate selection of patients for coronary-artery bypass grafting (CABG) is critical to ensure good outcomes. The evaluation of patients for CABG relies on a systematic assessment of the characteristics and coronary anatomy known to be associated with a survival benefit from CABG as compared with medical therapy or percutaneous coronary intervention (PCI). There is increasing evidence that treatment decisions for patients with complex coronary artery disease are best made through a process of shared decision making that includes the patient, the patient’s family, an interventional cardiologist, a cardiac surgeon, and ideally, the patient’s general cardiologist or primary care physician.
Stroke remains the most serious complication of CABG, occurring in 1 to 2% of patients in the perioperative period. Notable risk factors for stroke include a history of neurologic events, advanced age, peripheral or cerebrovascular disease, and diabetes. Aortic atherosclerosis is also a major risk factor for stroke after CABG because of the necessary manipulation or clamping of the ascending thoracic aorta. The use of a single aortic cross-clamp and epiaortic ultrasonography during CABG have been associated with a reduction in the risk of stroke over the past decade.
Patients with multivessel coronary artery disease and diabetes have an increased cardiovascular risk as compared with those without diabetes, and they have a survival benefit from CABG as compared with PCI. Patients with left ventricular dysfunction or mitral-valve disease also have an increased cardiovascular risk and have a survival benefit from CABG.
A. Recent trials and observational studies have updated previous work by including higher-risk patients and reflecting changes in practice. The most important was the SYNTAX study, which randomly assigned 1800 patients with either three-vessel or left main coronary artery disease to CABG or PCI. Evaluation of each participant included determination of the SYNTAX score (a measure of the extent and complexity of coronary artery disease) and the anticipated complexity of PCI. SYNTAX scores are used to classify the complexity of coronary artery disease as low (≤22), intermediate (23 to 32), or high (≥33). Overall, patients with three-vessel disease in the SYNTAX trial had a survival benefit with CABG as compared with PCI (rate of death, 9.2% vs. 14.6%, P=0.006). In patients with the least complex three-vessel disease (SYNTAX score ≤22), PCI was noninferior to CABG. In patients with more complex disease (SYNTAX score ≥23), CABG was superior to PCI. The survival benefit of CABG over PCI for patients with multivessel coronary artery disease has been confirmed in other studies and appears to be consistent when PCI is performed with second-generation drug-eluting stents. In the SYNTAX study, the outcomes of the two procedures were indistinguishable in patients with isolated left main coronary artery disease or left main coronary artery disease and single-vessel coronary artery disease (SYNTAX score <33). However, in patients with left main and two- or three-vessel coronary artery disease (SYNTAX score ≥33), there was a significant reduction in the rate of the composite end point of death, myocardial infarction, stroke, or repeat revascularization with CABG as compared with PCI (29.7% vs. 46.5%, P=0.003).
A. The evidence in favor of CABG is almost entirely based on studies of patients with stable ischemic heart disease. Nevertheless, the recommendations for CABG are commonly extended to include patients with acute coronary syndromes, including unstable angina and stable non–ST-segment elevation myocardial infarction. In practice, more than 60% of CABG procedures are performed during an acute care hospitalization and 29% follow a recent myocardial infarction. The best initial treatment for patients with acute ST-segment elevation myocardial infarction is reperfusion therapy with either PCI or fibrinolytic therapy. As compared with CABG, PCI restores coronary blood flow more rapidly, preserves myocardium, and improves outcomes. In this patient population, CABG is reserved for those who have a coronary anatomy that is not amenable to PCI or who have mechanical complications, such as ventricular septal defect, myocardial rupture, or papillary-muscle rupture with acute, severe mitral regurgitation.
Figure 1. Coronary-Artery Bypass Grafting.
Table 1. Indications for Coronary-Artery Bypass Grafting (CABG).